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A thin lens with centres of curvature C(...

A thin lens with centres of curvature `C_(1) and C_(2)` is shown in the figure given below. If the refractive index of material of lens is 1.5, calculate the focal length in cm.

Text Solution

Verified by Experts

From figure, first radius of curvature, `R_(1)=+5cm`
Second radius of curvature, `R_(2)=+15cm`
Refractive index of lens materal, `mu=1.5`
Focal length is given by
`(1)/(f)=(mu-1)[(1)/(R_(1))-(1)/(R_(2))]`
`=(1.5-1)[(1)/(5)-(1)/(15)]`
`=0.5xx(2)/(15)=(1)/(15)`
`rArr" "f=+15cm`
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